1. Field of the Invention
The present invention relates to a rack mountable T-shirt type handled plastic shopping bag and, more specifically, to a bagging system wherein bags are automatically opened when a preceding bag is removed from the rack. This invention also relates to a method of manufacturing the bags and bag packs.
2. Information Disclosure Statement
T-shirt type handled plastic bags have been commonly used in the grocery and retail product industries in the form of packs of such bags. The bag pack is mounted on a rack for consecutive dispensing of the bags and for holding the bag in an open position for loading articles. A conventional way of providing T-shirt type handled plastic shopping bags is to pack 50, 100 or more bags in a stack and bond the bags together by a hot pin welding. The hot pin usually welds the bags on their central tab which is an integral part of the bag, upwardly extending from the bag mouth. The bag pack is further mounted on a suitable supporting rack which includes at least a pair of lateral spaced support rods and a central mounting wicket to facilitate the bag dispensing. Usually, a finger sweep is made on the central tab to tear off the tab and open the bag mouth for loading merchandise. The QUIKMATE.RTM. bag/rack system is an example of a commercially available T-shirt bagging system. When the bag pack is mounted on the dispensing rack, the slippery and blocking nature of thin plastic film makes it difficult to manually open the bag for loading. A need therefore exists to dispense a bag easily while simultaneously and automatically opening and holding the next bag in a position to be loaded.
The prior art teaches various bagging systems to provide for the automatic opening of T-shirt type plastic bags. Different methods such as corona treatment, hot melt adhesives, coextrusion of different materials, etc. have been proposed to facilitate the opening of successive bags mounted on a dispensing rack.
Of these methods, perhaps the hot melt method is the most popular. The major disadvantage of this prior art is that the hot melt adhesive spot size, location, and applied amount is not easily controlled by the gun type applicator. The poor control of spot size and location affects the automatic opening of consecutive bags. For example, the spots must be aimed at a fairly broad area on the bag, such as below the mouth, to insure that the glue hits the bag. Such placement, however, is not optimum for opening a bag and can result in an oblong opening. Moreover, the hot melt gun often creates oversized adhesive spots which in turn produce a thick spot on the bag pack and tear a hole when the bag is pulled forward. Applying too much adhesive not only ruins bags, but also wastes adhesive, thus making the hot melt gun cost ineffective. On the other hand, the glue gun may fail to apply enough adhesive in which case the bag being removed disengages from the next bag before the next bag is opened. Extra slits in the bag's central tabs are often employed to ease the bag's separation from the rack and compensate for the lack of adhesive holding strength. The following is a summary of hot melt disclosures.
U.S. Pat. No. 2,715,493 to Vogt relates to square type handleless bags which are connected by a detachable hot melt adhesive bond. The bonds comprise narrow bands of adhesive at the open top which extend transversely across the entire opposed faces of the side walls of the adjacent bags. Likewise, U.S. Pat. No. 4,106,734 to Walitalo, is also directed to handleless plastic bags which are held in registration by employing a small area of adhesive below the bag mouth of the front ply of each bag. In addition to maintaining the bags in registration, the adhesive serves to partially open the bag mouth as each preceding bag is removed from the bag pack. The adhesive means used in both these disclosures, however, suffers the shortcomings mentioned above such as a lack of control over the position and amount of adhesive applied.
U.S. Pat. No. 4,676,378 and Re. 33,264 to Baxley et al, disclose a bag pack which features automatic opening of consecutive bags during the loading operation. Although Baxley further teaches suspending handle bags from suspension rods and utilizing an adhesive area just below the bag mouth region, the adhesive application technique disclosed is essentially the same technique as in U.S. Pat. No. 4,106,734. In addition to problems associated with hot melt adhesives, the Baxley invention also requires a slit in the central tab under the mounting aperture to insure proper severance form the central support wicket.
U.S. Pat. No. 5,020,750 and 5,125,604 to Vrooman, disclose a system for automatic consecutive opening and dispensing plastic grocery bags. The bag is opened by employing a spot of releasable hot melt adhesive bond below the bag mouth region in conjunction with a specially designed dispensing rack. In these references, the supporting rods of the dispensing rack are either made of two different materials of construction or extended at a predetermined angle such that the supporting rods provide the critical resistive force desired in this system. The releasable adhesive bond is applied by a gun type hot melt applicator. In these two references, the special designed dispensing rack is critical to the performance of consecutive bag opening. Moreover, these references have the same disadvantages as U.S. Pat. No. 4,676,378 such as poor control of the spot size, spot location, and amount of an adhesive.
U.S. Pat. No. 5,183,158 to Boyd et al., disclose a bag pack which features automatic opening of consecutive bags during the loading operation. The technique disclosed in this prior art is much the same as disclosed in U.S. Pat. No. 4,106,734 which speaks of suspending handle bags from suspension rods and utilizing an adhesive area just below the bag mouth region on the front of each bag in the bag pack. Boyd also teaches, however, adding another adhesive spot near the bottom of the bag, and applying a corona discharge and pressure treatment to the bag pack. These additional adhesion techniques increase the adhesion between the bags and promote fuller opening of individual bags. Nevertheless, other problems associated with the hot melt method remain.
U.S. Pat. No. 5,307,935 to Kemanjian, discloses a bag system for automatic consecutive opening and dispensing. This is accomplished by providing a special configuration for the central tab which has a narrow neck. The tab is partially slit between the neck edges and is adhered to the tabs of adjacent bags by a hot melt adhesive spot applied below the slit. The hot melt adhesive spot is applied by a gun type applicator which has several shortcomings as described above.
Aside from hot melt techniques, other inventions treat the plastic such that the side of one bag adheres to the side of the following bag. For example, U.S. Pat. No. 5,087,234 to Prader, like U.S. Pat. No. 5,183,158 to Boyd et al., discloses a technique of applying a corona discharge treatment to the bag mouth region. The pressure of cutting the bag mouth and handles causes this treatment to form a releasable link between the bags.
U.S. Pat. No. 5,013,290 to DeMatteis, discloses a method for producing sequentially opened T-shirt type plastic bags by utilizing coextruded bags having at least two layers wherein the inside layer has a low coefficient of friction and the outside layer has a high coefficient of friction. The prior art also includes a special means to cut off the front tab of each bag and create, on the rear tab, a slit that is perfectly horizontal and sufficiently close to the edge of the tab. The key characteristics are the relative stickiness and slipperiness of the various layers and the use of only the rear tab to hold the bag on the wicket.
Still other inventions disclosure using machinery to automatically open bags. For example, U.S. Pat. No. 3,243,937 to Ragan, presents an apparatus having an expandable mandrel on a conveyor and guide plate for the opening of square type handleless bags. The bags are connected in a chain by spots of separable adhesives between the sides of the bags near the open end. The series of bags arranged in flat face contact are further opened by the expandable mandrel in the apparatus.